Un-hardening Phenomenon of SCW

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• Un-hardening Phenomenon of SCW
• (Soil Cement Wall) Built in Organic Soils

Chung R. Song, Ph. D, PE
Department of Civil Engineering The University of
Mississippi University, MS 38677
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Presentation Order

• Job site description
• Problem description
• Researches
• Remedy

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Job Site DescriptionDeep Excavation

• East coast of South Korea (Samchuck)
• Deep Excavation D20m
• Strut SCW Wall
• Ground Condition
• -Fill GL.-0.5 to -0.7 m, Loose
• -Alluvium sands, silts, clays GL.-0.7 to 18.6
  m, N2 to 13
• -Weathered zone GL.-15.5 to -19.3, Ngt40

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Problem DescriptionConstructed SCW did not
solidified!!
Clayey soils were suspected as the culprit. Took
the clay samples and performed lab. tests.
No. Natural Water Content () Liquid Limit () USCS Organic Content ()
1 43 35.2 CL
2 44 33.2 OL N.A.
3 N.A. 39.2 OL 4.82
4 N.A. 34.2 OL 4.82
Based on lab. test results, the culprits were
narrow down to the clayey soil itself and organic
materials.
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Expected Strength of SCW
sand
qu (kg/cm2)
qu (kg/cm2)
clay
Curing Time, Day
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Typical Cures for Hardening Trouble of Clayey
Soils and Organic Soils
Item Chemicals
Clayey Soils Add cement, lime, NaOH, and(or) Ca(OH)2
Organic Soils Add cement, CaCl2, Ca(OH)2, and(or) NaSiO2
Lab. tests were carried out with above chemicals
mixed with field soils.
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Lab. Test Results
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Field Prescription Results
CaCl2 2 additional 22 cement was prescribed
considering the poor mixing condition in the
field. When applied to the job site, the SCW
walls were hardened nicely. Shovel excavation was
not possible.
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Conclusions

• SCW hardening trouble was caused by the organic
  clayey soil in the job site.
• To effectively control the hardening trouble in
  the job site, additional cement and Calcium
  chloride turned out to be most effective.
• Addition of Sodium silicate di-oxide increased
  the initial strength but decreased the long term
  strength, and therefore it was not prescribed for
  this project.